It is common practice in vineyards, for example, to use an elongate hollow guard placed around a young vine at the time of its planting to protect it during its early growth period. One such guard is described in the specification of Australian Patent Application No. 23516/92. This guard comprises a panel of flexible material adapted to be formed into a tubular body and releasably fastened in a tubular condition by means of cooperating tabs and slots provided along the vertical edges of the panel which are to be joined together. This allows the guard to be supplied as a blank in a flat, unfolded condition and subsequently formed into the tubular shape by a folding and interlocking operation
The guard disclosed in the specification has several disadvantages, including the difficulty of engaging the individual tabs into the appropriate slots. This is both time consuming and awkward particularly when the guard is of a length which makes it difficult to reach all tabs and slots.
U.S. Pat. No. 4,969,555 to Fitzgerald discloses another form of guard which uses fabric material having a plurality of sets of mating fasteners attached along opposite side edges thereof The material is placed around the base of a growing tree, and the bottom sets of mating fasteners are buckled around the trunk of the tree. Subsequently fasteners are in turn buckled which, in the case of a tree, progressively compresses the tree branches upwardly. This form of guard is relatively difficult to manufacture and requires substantial time and effort to engage in position.
U.S. Pat. No. 5,347,750 to Mills discloses plant protectors of a variety of forms including a form formed of extruded sheet material the opposite side edges of which are adapted to interlock. However, the edge portions of the panel material, in use, face in opposite directions and overly each other to enable one to be connected to the other. The join is, therefore, an overlapping join and disadvantage of this structure is the difficulty in interlocking the tab within the recess, particularly in the case of an elongated guard.
Another guard is described and illustrated in U.S. patent application No. 5,809,690. The guard of this patent is formed from a panel of plastics material which is folded into a tubular shape with adjacent vertical margins of the panel being connected together by means of a recallable zip type fastener which comprises fastener strips. Each strip has a locking profile portion which is adapt to releasably interlock with the locking profile portion of the other strip. The fastener strips arc secured to the opposite edge portions of the panel by heat welding or by means of an adhesive. The embodiments illustrated in the specification show the guard with an upstanding rear tab adapt to engage a wire of a wire trellis to secure the guard to the trellis.
The guards disclosed in the aforesaid prior patent specifications may be improved from the point of view of a user in terms of case and security of fasting together of the vertical margins of the guard panel. In particular, it has been found that the joining together of the vertical margins of the guard panel using cooperating tabs and slots is generally unsatisfactory in that the tabs, in some instances, become disengaged from their slots and gaps are created along the edges of the vertical margins. Such gaps allow entry points for chemical sprays such as herbicides, which can have a deleterious effect on a young plant.
It is also been found that the use of a zipper-type fastener as described in our U.S. Pat. No. 5,809,690 aforesaid, while a substantial improvement on tabs and slots and other fasteners for securing together the vertical margins of the guard panel, may also be unsatisfactory in some instances where pressure is exerted against the and of the fastener which may cause the fastener strips to disengage, particularly at the upper end. Thus, a vine within the guard may push against the upper edges of the fastener strips, or rest on the upper edges, and cause the strips to disengage.